1. Field on the Invention
The present invention relates in general to windcone lighting devices and, in particular, to swivel devices.
2. Description of the Prior Art
Various types of windcones to indicate wind direction and velocity have been in use at airports around the world. Normally, these windcones, being rotatably about a vertical axis mounted on an upright pole, utilize a truncated conical framework provided with a windsock. The air current passing through the windsock causes it to distend leewardly and point windwardly. The degree of expansion of a windsock, by the wind passage, constitutes an indicator of the wind velocity.
Since aircraft landing occurs both in daylight and at night, it is critical that windcones be well illuminated for night time visibility. Therefore, a lighting fixture, comprising a bulb, is adapted to illuminate the interior of the windsock directly, and thereby, to provide an indication of the wind direction and velocity, even in hours of darkness. The windsock is formed from a suitable fabric material, so that the light rays from the bulb would be visible through the cone.
As can be seen from the above, the use of a single light, that directly illuminates the windcone with which it rotates, provides adequate illumination, regardless of the wind direction
The connection between the upper part of the fixed upright pole and the rotatably mounted windcone and the connection between a fixed electrical power supply and the light fixture, which rotates with the cone, is provided by a swivel device. This device, which constitutes the most important part of a windcone assembly, is exceptionally vulnerable due to its direct exposure to unobstructed heavy wind, rain, snow and, implicitly, changes of temperature.
Attempts have been made in the past to introduce a better swivel device. U.S. Pat. No. 4,553,430, dated Nov. 19, 1985 and granted to Behrens for "Illuminated windsocks for airports" teaches the use of a spotlight bulb directed along the horizontal axis of the windsock. The bulb may be mounted directly to a rotating axle, coaxially with the supporting post, or can be carried by radial arms attached to the circular framework of the windsock. There are obvious disadvantages to Behren's design. First, the electrical fixture, used for illumination, is energized by electrical conductors which terminate in conventional alligator-type electric clips, slidably attached to a slip ring assembly. It is known that the use of brushes is more reliable and efficient. Second, use is made of an upright axle with upper and lower bearings, rotatably supported on the axle. Each of the bearings has a radially extending rod which is welded to a rim of windsock framework. Thus, the distance between the bearings is substantial, the length of the upright axle being commensurate with the larger diameter of the windsock. Due to this design and to the fact that the assembly, alligator clips-slip rings, is located beyond the two bearings, above the upper one, this device lacks compactness.
U.S. Pat. No. 4,486,754, dated Dec. 4, 1984 and granted to Guggemos for a "Lighted windcone for evacuation aid" discloses a windcone lighting device. Here, a tubular shaft is mounted on top of an upright pole, firmly attached to a base. The windcone is rotatably mounted on the tubular shaft, the mounting comprising a pair of vertically spaced bearings. A bracket is attached to each outer race of these bearings for joining and rotating with the windcone. An assembly, slip rings-brushes is located above the upper bearing. A lamp support conduit, which assumes a generally "J" shape, connects the brushes to a light and rotates with the windcone. In another embodiment, there is lamp support located between the brackets, within the windcone. Guggemos structure has the same shortcomings as Behrens structure Moreover, the use of a lamp support conduit or a lamp support which do not form a unitary rigid structure with the slip rings-brushes assembly constitutes another shortcoming.